The present invention concerns an improved apparatus for isolating a pressure sensitive device from blood flowing in an extracorporeal blood system and for transmitting the blood pressure to the pressure sensing device.
In a typical extracorporeal blood system, such as dialysis or oxygenation for example, blood is pumped from a patient through a bubble trap, through the mass transfer device (such as the dialyzer or the oxygenator), through a bubble trap and back to the patient. The blood pressures in the line are typically monitored using one or more pressure sensitive transducers. The transducers are isolated from the blood flow line by means of a isolating device which may be coupled between the blood flow line and the pressure sensitive transducer. The isolating device must be operable to protect the transducer, to provide a sterile barrier and to transmit the blood pressure to the transducer.
One type of isolating and blood pressure transmitting device is disclosed in Gangemi, U.S. Pat. No. 4,077,882, issued Mar. 7, 1978. I have discovered an isolating device that is superior in construction and operation with respect to the device disclosed in the Gangemi U.S. Patent, in that the present invention is more compact in construction and thus provides packaging advantages, has a construction which leads to a superior membrane displacement thus resulting in less head pressure losses and a more accurate pressure transmission, and has a construction which provides a significantly greater air volume displacement for a full membrane displacement.
Therefore, it is an object of the present invention to provide an isolating and blood pressure transmitting device that is simple in construction and is easy to manufacture.
Another object of the present invention is to provide an isolating and blood transmitting apparatus that is compact in construction and provides packaging advantages.
A further object of the present invention is to provide an isolating and blood transmitting apparatus that may be produced either by injection molding or thermo-forming.
A still further object of the present invention is to provide isolating and blood transmitting apparatus that enables a relatively accurate pressure transmission.
Another object of the present invention is to provide an isolating and blood transmitting apparatus that has a relatively large air volume displaced for the full membrane displacement, enabling the apparatus to be connected to a pressure-monitoring device having a large internal volume, or enabling use with a long connecting tube without sacrificing the precision and the upper limit of the applicable pressure.
Other objects and advantages of the present invention will become apparent as the description proceeds.